When a sewing machine needle is to be changed, or a thread is to be set in the eye of the needle, the presser foot of the sewing machine is lifted, and its pressing action released, by lifting a presser foot lifting lever and the presser foot lifting lever is rotated outward around a presser bar to provide enough space for an operator to perform the aforementioned manual tasks.
Under such circumstances, the usual practice has been to design the sewing machine so as not to start even if the operator unintentionally attempts to start it. The sewing machine is designed so that the presser bar guide bracket is engaged with the needle bar preventing the sewing machine from starting. The needle bar is stopped by the presser bar guide bracket.
In conventional sewing machines, if the presser foot is pressing, by means of its presser spring, the workpiece against the machine bed for stitching, and if the workpiece is thick in whole or part, the presser foot is raised up to the same level as if lifted by the presser foot lifting lever and the presser bar guide bracket is derailed from its guide slit. Under such conditions, the presser foot tends to rotate outward around the presser bar because of machine vibration or due to the outward component of the work feeding force. As a result, the needle bar strikes against the presser bar guide and the parts are damaged.